Track disabling/enabling

Hello,

currently muted tracks aren't processed and don't take CPU cycles only if "don't process muted tracks" option is on; with this option on, some nasty artifacts can be heard unmuting tracks with plugins having fairly high latency.

In addition, in order to help separating tracks actively in the project from other ones that are in the project but don't need to be processed, I think it would be great being able to disable tracks.

Disabling a track (possible only with transport stopped) the following things happen:

- Track data isn't played nor processed anymore
- All track FXs are bypassed and, optionally, put offline
- All track sends and receive are disabled

Re-enabling the track brings it back to the mix, preserving its original mute, solo and send status; again, to avoid any possible audio glitch, re-enabling can be done only with transport stopped.

This function is present and very useful in other hosts, for example Cubase and SONAR; on the latter it is called "archive".

Discussion thread here:

http://forum.cockos.com/showthread.php?t=41656

Thanks,
Mario